I arbitrarily drew it out of the corner at 45 degrees, and I don't claim that it's exactly accurate. But, it represents the general idea. Just look at how big Hargis is compared to JFK. It has to be the case that that distance was additive to the photographer.
But, it makes no sense at all for Mary to have done it. She was prepared to take her picture from the moment the limo rounded the corner and started coming down the hill. The idea that she would have let it reach her without snapping the shutter is ridiculous. It made the most sense for her to do it slightly before they reached her. Why? Because that way she could capture their faces, and that's the most desired thing to catch. But, if she waited until they were directly opposite her in the street and shot them in profile, she might have gone for that. But, to let them pass her, after waiting so long, only to shoot the backs of their heads? No frickin' way. She wouldn't do that. Nobody would.
But, Babushka Lady's situation was different. She was behind Charles Brehm, who was blocking her view. But, as we can see in the Muchmore film, she stayed behind him and shot the Kennedys diagonally to her right as they were approaching her. But then, when they passed in front of Brehm, they were lost to her, so she repositioned herself, turning left, and setting herself up to shoot them diagonally to her left. And when they came into view, she took another picture, and she apparently took more than one picture. We can see her doing it in the Muchmore film.
When you think about what she would have captured shooting at that moment, the Moorman photo fits the bill nicely.
But, the point is that she did, in fact, do what we know the taker of the Moorman photo did. That is absolutely certain. The result, the Moorman photo, meets all the conditions and characteristics to be her photograph. The idea that Mary Moorman would have done this or did this is preposterous. There is no chance that she did. She simply didn't take it.